LabMed

Bartter Syndrome

At a Glance

Bartter syndrome is a clinical condition associated with chronic metabolic alkalosis and hypokalemia. As opposed to Gitelman syndrome, Bartter syndrome has a normal serum magnesium (see section on Gitelman syndrome). The age of onset of clinical symptoms is within the first few years of life with the findings of polyuria and polydipsia, frequent dehydration, muscle cramps, and weakness. These patients often have salt craving to help replete intravascular volume. This is a genetic, recessive disorder and can be diagnosed prenatally.

This may be mistaken as familial hypokalemic paralysis (FHP), which is an autosomal dominant disease. FHP has intermittent hypokalemia with normal urinary potassium and normal total body potassium stores.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Low specific gravity of the urine with elevated urinary potassium levels with evidence of normal plasma renal function, normal calcium, phosphorous, and magnesium, and evidence of a hypokalemic metabolic alkalosis are current findings. Further measurement of the plasma renin and aldosterone levels shows evidence of elevated levels in the face of the chemistry finding noted in the first line.(Table 1)

Table 1

Laboratory findingsof evidence of a hypokalemic metabolic alkalosis with high urinary CL and Potassium

Genetic Testing forBartterSyndrome can be found at (http://www.ncbi.nlm.nih.gov/sites/GeneTests)

PRESENT

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Whereas there are no facts that may effect this lab tests, there are some clinical conditions that may mimic Bartter syndrome These may include diuretic use, vomiting, cystic fibrosis, or chronic respiratory with CO2 retention.

What Lab Results Are Absolutely Confirmatory?

Exclusion of other causes of hypokalemic metabolic alkalosis and, in some cases, genetic testing are confirmatory.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

The clinical findings of hypokalemic metabolic alkalosis with exclusions of other causes with evidence of high levels of urinary Potassium and Chloride confirm this diagnosis. Gene testing as suggested in the table may confirm this but for the most part it is a diagnosis that contains the constellation of findings with the exclusion of other diseases that may mimic Bartter syndrome.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Any drug that affects the renal angiotensin system, in theory, may affect the renal wasting of CL and K and may mimic Bartter syndrome.